The ACTU Virology Core laboratory has and will continue to play an essential role in the evaluation of experimental antiviral treatment for HIV-1 infection in the ACTG. The development and evaluation of effective therapies for HIV-1 infection is limited by the long time interval to clinical endpoints. In addition, enrollment of infants of seropositive mothers into clinical trials is limited by the difficulty in diagnosing HIV-1 infection due to placental transfer of maternal HIV-1 antibody. Therefore, the availability of virological assays is needed to 1) assess the effect of antiviral drug therapies on viral load and viral resistance and 2) diagnose HIV-1 infection in seropositive infants. The proposed study has the following specific aims: 1. To provide regional laboratory support for ACTG protocol-mandated virology testing including culture of Human Immunodeficiency Virus Type 1 (HIV-1) and measurement of HIV-1 p24 antigen levels from clinical samples. 2. To evaluate new clinically relevant HIV-1 virological markers for implementation in ACTG protocols. The Case Western Reserve University (CWRU) ACTU Virology laboratory is certified to provide HIV-1 culture testing and measurement of serum HIV-1 p24 antigen levels for ACTG protocols. The laboratory has the capacity to perform up to 1000 HIV-1 cultures and 5000 serum HIV-1 p24 antigen levels per year. In addition, the laboratory is currently performing quantitative HIV-1 plasma and cell cultures, qualitative and quantitative HIV-1 nonisotopic polymerase chain reaction (PCR) assays, and serum p24 antigen assays after acid treatment. The CWRU ACTU Virology laboratory has the capacity and expertise to become and ACTG regional virology core laboratory.